Regulating and filtering transformer having a magnetic core constructed to facilitate adjustment of non-magnetic gaps therein

ABSTRACT

A parametric regulating and filtering transformer including a magnetic core having input, output and saturating regions, input and output windings disposed in inductive relation with the input and output regions, and a capacitor connected to the output winding to provide a tank circuit. Different embodiments of the parametric transformer develop a non-magnetic gap or gaps, in the output region of the magnetic core, required to provide the desired waveform and electrical performance of the transformer, while facilitating the manufacture and assembly of the transformer.

United States Patent Spreadbury {451 *Aug. 22, 1972 [54] REGULATING AND FILTERING [56] References Cited TRANSFORMER HAVING A UNIIED PA MAGNETIC CORE CONSTRUCTED TO 3 584 290 6/1971 TENTS 323/6 FACILITATE AD USTMENT OF prea ury Henderson X 2,561,855 7/1951 Gould ..336/l65 [72] Inven or: Ro r J- Spreadbury, Murrysville, 2,630,478 3/1953 Howlett ..336/165 Pa. 2,668,250 2/1954 Henderson ..336/ 165 X Assigneez Westinghouse Electric Corporation 3,579,088 7/1971 Fletcher et a1 ..323/6 Pmsburgh, Primary Examiner-A. D. Pellinen 1 Notice; The portion f the term f this Attorney-A. T. Stratton, F. E. Browder and Donald patent subsequent to June 6, I988, Lackey .2 'l i iiiiif ABSTRACT 1 le pr A parametric regulating and filtering transformer in- [21] Appl. No.: 136,701 cluding a magnetic core having input, output and saturating regions, input and output windings disposed in inductive relation with the input and output regions, [52] US. Cl. ..323/6, 323/60, 336/165, and a capacitor connected to the Output winding to 336/170 336/215 provide a tank circuit. Different embodiments of the [51] Int. Cl ..G05f 3/06 parametric transformer develop a non magnetic gap Fleld of Search 44, 60, or gaps in the output region of the magnetic core 215 required to provide the desired waveform and electri- TO A.C. POTENTIAL cal performance of the transformer, while facilitating the manufacture and assembly of the transformer.

17 Claims, 14 Drawing Figures AAPACITOR a LOAD Patented Aug. 22, 1972 4 Sheets-Sheet l EQE Q Patented Aug. 22, 1972 4 Sheets-Sheet 5 wow mON

Patented Aug. 22, 1972 3,686,561

' 4 Shegts-Sheet 4 Q o L:

J 6 a 31 w [I g H q |I l?? E 3] HIII 6 T fil REGULATING AND FILTERING TRANSFORMER HAVING A MAGNETIC CORE CONSTRUCTED TO FACILITATE ADJUSTMENT OF NON-MAGNETIC GAPS THEREIN BACKGROUND OF THE INVENTION Field of the Invention The invention relates in general to regulating transformers, and more specifically to regulating and filtering transformers of the parametric type.

Description of the Prior Art Co-pending application, Ser. No. 835,953 filed June 24, 1969, now US. Pat. 3,584,290 which is assigned to the same assignee as the present application, discloses a new and improved three-path regulating transformer of the parametric type. This new and improved regulating transformer requires a magnetic core having input, output, and saturable regions, provided by three spaced parallel leg portions, input and output windings disposed in inductive relation with the input and output regions of the magnetic core, and a capacitor connected to the output winding to provide a tank circuit. The alternating fluxes produced in the input and output regions, dictated by a source of alternating potential connected to the input winding, and the capacitor voltage, respectively, share the saturable region, with negligible direct .flux linkage of the input and output windings, until the vector addition of these parallel fluxes reaches a magnitude sufficient to saturate the saturable region. When the saturable region reaches saturation, which is typically for about of each half cycle of the source potential, the flux produced by the input winding is forced through the output region, linking the output winding and thus transferring energy into the tank circuit to sustain oscillation thereof. The short period of direct transformer coupling, and the fact that the direct coupling occurs near the voltage zero of the output voltage waveform, provides excellent filtering of any noise in the input voltage waveform, and the output voltage is regulated to :':().5 percent for a :15 percent change in input voltage from nominal, without closed loop control.

While this three path parametric transformer may be constructed without a non-magnetic gap in the output region of the magnetic core, by proper dimensioning of the magnetic core, in practice the output region is gapped as it optimizes the output voltage waveform from the standpoint of harmonic content, it increases the stability of the transformer, it enhances the decoupling of the input and output windings, and it controls many operating characteristics of the transformer, such as the threshold level of the input voltage required to start the operation of the transformer. Selfstarting at a predetermined voltage less than the nominal input voltage may be achieved by selecting a gap dimension which is about mils per square inch of cross-sectional area of the output leg of the magnetic core.

The magnetic core of the three-path parametric transformer has first, second and third spaced parallel leg portions interconnected by first and second yoke portions. When the magnetic core is wound from magnetic, metallic strip material, the resulting loop is cut transversely to the leg portions of the core to enable the input and output windings to be assembled therewith, and the desired gap in the output region of the magnetic core is formed by machining a cut end of the leg which is to function as part of the output region of the magnetic core. This manufacturing approach effectively presets the non-magnetic gap dimension and thus 5 limits the amount of adjustment available to take care SUMMARY OF THE INVENTION Briefly, the present invention is a new and improved parametric regulating and filtering transformer, and methods of constructing same, which provides a nonmagnetic gap in the output region of the'magnetic core without machining the gap. In one embodiment of the invention, the magnetic core is wound from a magnetic, metallic strip material to provide first, second and third spaced parallel leg portions, and instead of cutting the magnetic core transversely to the leg portions, the first and third leg portions are severed from the intermediate portion of the magnetic core by cutting each yoke portion transversely at two predetermined spaced locations. The input and output windings are assembled with the first and third leg portions and the legs reassembled with the intermediate portion of the core, with non-magnetic spacer means being disposed between the cut portions of the third leg and the complementary cut portions of the intermediate core portion.

In other embodiments of the invention an independent magnetic shunt, in the form of a packet or stack of magnetic, metallic laminations is used to facilitate the manufacture of the magnetic core, with both wound and stacked type core constructions.

In another embodiment of the invention, modified E- and L-shaped laminations are assembled to provide a magnetic core having a non-magnetic gap in the output .region of the core, while alternating the orientation of the laminations from layer to layer to improve the core magnetically and mechanically.

BRIEF DESCRIPTION OF THE DRAWINGS The invention may be better understood, and further advantages and uses thereof more readily apparent, when considered in view of the following detailed description of exemplary embodiments, taken with the accompanying drawings, in which:

FIG. 1 is a partially schematic view of a parametric regulating transformer which may advantageously utilize the teachings of the invention;

FIG. 2 is a perspective view of a wound magnetic core which may be utilized in a three-path parametric transformer, illustrating the cutting thereof according to the teachings of the invention;

FIG. 3 is an exploded perspective view of a parametric transformer constructed with the magnetic core shown in FIG. 2',

FIG. 4 is a perspective view of the transformer shown in FIG. 3, after assembly;

FIG. 5 is a perspective view of a magnetic core for a parametric transformer constructed according to the teachings of the invention, using two wound C-cores and a magnetic shunt;

FIG. 6 is a perspective view of a magnetic core for a parametric transformer constructed according to the teachings of the invention, using two stacked C-cores and a magnetic shunt;

FIG. 7 is a partially schematic view of a parametric regulating transfonner having a magnetic core which includes two C-cores and a magnetic shunt;

FIG. 8 is a perspective view of a magnetic core for a parametric regulating transformer constructed according to the teachings of the invention, using a wound core having three leg portions and a magnetic shunt;

FIG. 9 is a perspective view of a magnetic core for a parametric regulating transformer constructed according to the teachings of the invention, having two core sections each formed of E-shaped laminations, and a magnetic shunt;

FIG. 10 is a partially schematic view of a parametric transformer constructed with the magnetic core shown in FIG. 9;

FIG. 11 is a perspective view of a magnetic core for a parametric transformer constructed according to the teachings of the invention, using four C-cores and a magnetic shunt;

FIG. 12 is a perspective view of a magnetic core for a parametric regulating transformer constructed according to the teachings of the invention, having two core sections formed of E-shaped laminations and a magnetic shunt, with the middle leg of the E-shaped laminations being wider than the outer legs thereof;

FIG. 13 is a partially schematic view of a parametric regulating transformer constructed with the magnetic core shown in FIG. 12; and

FIG. 14 is a perspective view of a parametric regulating transformer constructed according to the teachings of the invention, having a magnetic core formed of modified E- and L-shaped laminations.

DESCRIPTION OF PREFERRED EMBODIMENTS Referring now to the drawings, and FIG. 1 in particular, there is shown a three-path parametric regulating and filtering transformer of the core-form type, constructed according to an embodiment of the hereinbefore mentioned co-pending patent application. Transfonner 20 includes a magnetic core 22, having first, second and third connected regions 24, 26 and 28, provided by first, second and third spaced, parallel leg portions, respectively. The adjacent ends of the regions are joined by upper and lower yoke portions 30 and 32, respectively, defining first and second windows or openings 34 and 36, respectively. Magnetic core 20 is wound from magnetic, metallic strip material, such as grain oriented silicon steel, to provide a plurality of nested turns 33 which encircle the first window 34, a plurality of nested turns 35 which encircle the second window 36, and a plurality of nested turns 37 which encircle the turns 35 and 37, and therefore both of the windows. The first and third regions 24 and 28 are outer legs of the magnetic core structure 22, and the second region 26 is an inner leg. The first and third re gions 24 and 28 are substantially non-saturating input and output regions, respectively, and the second region is a common saturable region.

Magnetic core 22 has three magnetic loops or paths, with the first magnetic path encircling the first window 34 via the first or input region 24, a portion of the lower yoke 32, the second or saturable region 26, and a portion of the upper yoke 30. The second magnetic path encircles the second window 36 via the second or saturable region 26, a portion of the lower yoke 32, the third or output region 28, and a portion of the upper yoke 30. The third magnetic path encircles both the openings 34 and 36 via the first or input region 24, the lower yoke portion 32, the third or output region 28, and the upper yoke portion 30.

Means 44, including a primary or input winding 46, and a source 48 of alternating potential, are connected to provide a first alternating flux in the first magnetic path, and means 50, including a secondary or output winding 52 and a capacitor 54, is connected to provide a second alternating flux in the second magnetic path. Means 50 is a tank circuit, with a load circuit 56 being connected across the parallel connected output winding 52 and capacitor 54.

It is critical for the proper operation of the regulating transformer 20 that the magnetic core 22 be constructed such that the second or common region 26 be saturable at a point less than the vector sum of the first and second alternating fluxes, and that the input and output regions 24 and 28 be substantially non-saturating within the design range of the fluxes which will link them. The input and output windings 46 and 52, respectively, in conjunction with the capacitor 54, automatically insures that the alternating flux in the input and output regions adds substantially inphase in the common saturable region 26 to saturate the common region during a portion of each half cycle of the alternating flux therein. The magnetic core 22 is constructed with the reluctances of the first and third magnetic paths such that the major portion of the flux produced by means 44 will follow the first magnetic loop or path, while still providing sufficient flux in the third magnetic loop or path to directly link the input and output windings, and induce a voltage in the output winding 52 sufficient to charge capacitor 54 to the point necessary to make the regulating transformer 20 self-starting.

The common saturating region 26 of magnetic core 22 reaches saturation during each half cycle of the alternating source potential 48, with the flux provided by means 44 adding to the flux provided by the tank circuit 50 in region 26 during one half cycle, and then the flux provided by means 44 and 50 both reverse their direction, still additive in the common saturable region 26, but in the opposite direction, to drive region 26 into saturation during this half cycle.

When source potential 48 is connected to input winding 44, an alternating flux will be produced which divides between the first and third magnetic paths according to their relative reluctances, with the geometry of the core dictating relatively weak direct transformer coupling between the input and output windings 46 and 50 via the third magnetic path, and a much stronger flux in the first magnetic path. The weak transformer coupling between the input and output windings, however, is unopposed by flux provided by the tank circuit 50 during startup, and thus the regulating transformer may be constructed to induce sufficient voltage into output winding 52 to charge capacitor 54 to the magnitude necessary to start and sustain oscillations in the tank circuit 50. The threshold voltage necessary to start and sustain oscillations in the tank circuit 50 depends upon the magnitude of the load across the tank circuit. Once the tank circuit starts to oscillate, its flux in the second magnetic path adds to the flux provided by means 44 in the common saturable region 26, driving region 26 to the knee of its hysteresis curve. Upon reaching saturation, region 26 is no longer a low reluctance path for the flux provided by means 44, forcing the flux provided by means 44 around'the third magnetic path, strongly coupling the input and output windings 46 and 52 and inducing a voltage into the output winding 52 which charges capacitor 54 to provide the energy required to sustain the oscillations of the tank circuit. Region 26 only stays in saturation for a few degrees, typically less than 15, of the half cycle of the source potential, with the strong transformer coupling occurring only during this very short interval of time. During the remaining portions of each half cycle of the source potential, the input and output windings are effectively isolated. Thus, it will be readily understood that the output voltage waveform is not substantially affected by noise in the input voltage waveform. For a cyclic disturbance, i.e., waveform distortion and/or periodic spikes, the regulating transformer will integrate the overall energy level and provide afiltered, stable output voltage.

A non-magnetic gap 60 is provided in the output re gion 28, which linearizes the output region and changes the output waveform of the tank circuit '50 from substantially a square wave to a sine wave. Thus, the dimension of gap 60 controls the harmonic content in the output voltage waveform. The gap 60 also eliminates the possibility of low frequency amplitude modulation of the desired output voltage, and it improves the stability of the tank circuit. Further, it

enhances the decoupling of the input and output windings 46 and 52, respectively.

The dimension of gap :60 is somewhat of a compromise between harmonic content of the output voltage waveform, and power capability of the parametric regulating transformer, with a dimension of about 20 mils per square inch of cross-sectional area of the output leg providing a good sine wave output voltage without undue sacrifice of power output capability.

In the manufacture of parametric regulating transformers, variations in the magnetic materials and windings, and capacitor tolerance, often make it necessary to establish the dimension of gap 60 during tests. This is difficult for unskilled personnel, as the gap 60 is usually disposed within the confines of the output winding 52. Further, the gap dimension is established by a relatively costly machining operation, after the magnetic core 20 is cut into two halves along a centerline or axis disposed perpendicularly through the three legs of the wound core. If the first gap dimension selected is too small, the magnetic core input and output windings are disassembled and the cut end of one of the halves is machined again to remove additional material. If the gap dimension selected is too great, the magnetic core is a costly reject.

The first embodiment of the invention discloses a new and improved parametric regulating transformer of the core-form type, having a wound magnetic core which provides the required gap in the output region without machining, while facilitating the manufacture, assembly and test of the transformer. FIG. 2 is a perspective view of a magnetic core 62 which is cut according to the teachings of the invention. Magnetic core 62 is wound in the same manner as magnetic core 20 shown in FIG. 1, and it includes first, second and third leg portions 64, 66 and 68, respectively, and upper and lower yoke portions 70 and 72, respectively, all of which cooperate to define first and second windows 74 and 76, respectively, for receiving portions of the input and output windings.

Instead of transversely cutting the three leg portions of the magnetic core, along a common cut-plane, as illustrated in FIG. 1, this embodiment of the invention teaches cutting each yoke portion transversely thereto at twopredetermined spaced locations, with the predetermined spaced locations being selected to sever the first and third leg portions 64 and 68 from the intermediate portion of the magnetic core 62. Very little yoke is included with the severed first and third leg portions 64 and 68. The selected cut planes intersect the windows 74 and 76 immediately adjacent to where the severed legs join the yoke portions. If the corners of the windows are curved, such as illustrated at corner 78, the point of intersection of each cut plane with a window is preferably where the curved corner ends and the straight portion of the window which defines the yoke begins. Thus, as indicated in FIG. 2, yoke 70 is cut transversely along the two spaced out planes indicated by arrows 80- 80, respectively, and yoke 72 is cut transversely along two spaced cut planes indicated by arrow 84 and arrows 86-86'. Although four total cuts are involved, only two cutting steps are required to make the four cuts, as the two cut planes for severing each leg portion are in alignment. Thus, the cut planes represented by arrows 80-80 and 84 are in alignment, and the cut planes represented by arrows 82 82' and 8686 are in alignment.

FIG. 3 is an exploded perspective view of a parametric regulating transformer 90, constructed with the magnetic core 62 shown in FIG. 2. After the step of cutting the magnetic core 62 to sever the outer leg portions 64 and 68 from the intermediate portion of the magnetic core, which includes the intermediate leg 66 and yoke portions 70 and 72, input and output windings 92 and 94, respectively, are provided, which are telescoped over the first and third leg portions 64 and 68, respectively. The first leg portion 64 may then be reassembled with the intermediate portion of the magnetic core, with their complementary cut portions being butted together. The third leg portion 68 is also reassembled with the intermediate portion of the magnetic core, but instead of butting the complementary cut portions tightly together, they are spaced apart by a predetermined dimension to provide the required total gap dimension in the output loop of the parametric regulating transformer 90. While the dimensions of the two gaps, i.e., the gap between yoke 70 and leg 68, and the gap between yoke 72 and leg 68, are preferably the same in order to simplify the manufacture and assembly of the transformer 90, they may be different if desired. The gaps are established and maintained by insetting insulating spacer members 96 and 98 between the cut portions of yokes 70 and 72, respectively, and the complementary cut portions of leg 68, as the leg 68 is assembled with the intermediate portion of the core 62. Insulating spacer members 96 and 98 may be formed of any suitable material which will maintain their dimensions in the operating environment of the transformer 90, such as one of the laminated plastic materials.

The combined gap dimensions may be greater than the preferred 20 mils per square inch of cross-sectional area of the output leg, as this value was established for a single non-magnetic gap disposed within the output winding. When the gap or gaps are disposed outside of the output winding, there is more flux fringing at the gap.

FIG. 4 is a perspective view of transformer 90 after assembly, illustrating that the three separable sections of the magnetic core 62, and the input and output windings 92 and 94, respectively, may be easily held in assembled relation by a conventional core band 100. The transformer 90 is complete in FIG. 4, except for connecting a capacitor (not shown) to the output winding 94 to provide a tank circuit.

It should be noted that the gaps in the output loop of magnetic core 62 are established and maintained without requiring an additional machining step. The gap dimensions are easily established, merely by selecting the thickness dimension, or dimensions, of the insulating spacer members 96 and 98. Establishing different gap dimensions merely requires selecting spacer members having the desired dimensions.

The non-magnetic gap may also be easily established and maintained in the output loop of the magnetic core of a three path parametric regulating transformer, by constructing a separate or discrete magnetic shunt and assembling it with easily manufactured and assembled core elements or components. FIGS. 5, 6 and 7 illustrate an embodiment of the invention which illustrates the use of a magnetic shunt with core-form construcnon.

More specifically, FIG. is a perspective view of a magnetic core 110 for a core-form parametric regulating transformer, which utilizes a discrete magnetic shunt 112, first and second wound C-cores 114 and 116, respectively, and insulating spacer means 118 which establishes and maintains first and second nonmagnetic gaps 120 and 122 in the output loop portion of magnetic core 110.

The magnetic shunt 112 is formed of a plurality of thin, rectangularly shaped larninations 124 which are superposed to provide a stack of larninations, with the integrity of the stack being maintained for easy handling by bonding the larninations together. The laminations 124 are preferably formed of grain oriented magnetic material, such as silicon steel, having at least one preferred direction of magnetic orientation. The at least one direction of magnetic orientation should be parallel with the longitudinal axis of the laminations. For 60 H3. applications, the larninations are preferably formed of magnetic material having a thickness dimension of about 12 mils.

The first and second C-cores 114 and 116 may be formed by winding a strip of grain oriented steel into a rectangular or circular loop having the desired window dimensions and number of turns, bonding the nested turns of the loop together, and then cutting the loop to provide first and second C-cores. Since the output winding requires more window volume than the input winding, the wound loop is preferably designed such that it may be cut ofi-center, and provide close fitting windows for both the input and output windings.

In the assembly of the magnetic core 110, an input winding (not shown) is telescoped or slipped over one leg of C-core 114, such as over leg 126, and the resulting assembly has the cut ends of the legs of the C-core butted tightly against one side of magnetic shunt 112, with the selected side of the shunt preferably being one of the sides formed by the edges of the stack of laminations.

An output winding (not shown) is telescoped over one leg of C-core 116, such as leg 128, but instead of butting the cut ends of the legs of C-core 116 directly against the magnetic shunt 112, the insulating spacer member 118 is disposed against the side of the shunt which is opposite to that associated with the first C- core, and the cut ends of the C-core 116 are butted tightly against the insulating spacer member 118. Since the insulating spacer 118, in this embodiment, is not disposed inside a winding opening, it may be in the form of a single sheet, as illustrated, instead of using two members which are sized to closely fit the gap created between the assembled core members. However, the gaps 120 and 122 may be formed by using two separate spacer members, if desired.

In the assembly of magnetic core 110, the cut ends of the two C-cores 114 and 116 are aligned, just as they were prior to cutting, i.e., legs 126 and 128 are aligned with one another, and the remaining legs are aligned with one another, enabling the resulting assembly to be easily banded to hold the various core members and windings in the desired assembled relation.

FIG. 6 is a perspective view of a magnetic core which is similar to magnetic core 110 shown in FIG. 5, except the two C-eores are formed of a plurality of C- shaped larninations, bonded together and stacked. Like reference numerals in FIGS. 5 and 6 indicate like components, and like reference numerals except for a prime mark in FIG. 6 indicate like functions but slightly modified structure.

More specifically, magnetic core 1 10 includes a magnetic shunt 112 and an insulating spacer member 118, as hereinbefore described relative to FIG. 5, and first and second C-core members 114' and 116', respectively. The Score member 114' is constructed of a plurality of substantially C-shaped magnetic, metallic larninations 1 15, and C-core member 116' is constructed of a plurality of substantially C-shaped magnetic metallic larninations 117. In order to provide closely fitting windows or openings for the input and output windings, the length dimensions of the C-shaped larninations may be different for the first and second C-cores 114' and 116. In other words, the length of the leg portions of the C-shaped larninations for core section 114' is preferably less than the length of the leg portions of the C-shaped larninations for the magnetic core section 116. The assembly of the magnetic core with associated input and output windings is the same as described relative to FIG. 5.

FIG. 7 is a partially schematic view of a core-form parametric regulating transformer 130 constructed with the magnetic core 110 shown in FIG. 6, but the construction would also be the same when using the magnetic core 110 shown in FIG. 5. An input winding 132 is disposed about leg 126 of the first C-core 114', with the input windingl32 being adapted for connection to a source 134 of alternating potential. The ends of the outwardly extending legs of the first C-core 114 are butted tightly against the magnetic shunt 112. An output winding 136 is disposed about leg 128 of C- core 116, and a capacitor 138 is connected to the output winding 136 to provide a tank circuit. The output winding may also be adapted for connection to a load circuit 140. The capacitor and load voltages need not be the same. For example, as illustrated, the capacitor 138 may be connected across only a predetermined portion of the output winding 136.

The insulating spacer member 118 is disposed on the side of the magnetic shunt 112 which is opposite to the side associated with the first C-core 114, and the second C-core 116 is butted against the insulating spacer member 118 such that its legs are aligned with the legs of the first C-core 114'. The first magnetic loop, through which the flux provided by winding 132 is primarily directed, thus includes the first C-core and the magnetic shunt 112, and the second magnetic loop, through which the flux provided by the output winding 136 is primarily directed, includes the second C-core 116 and the magnetic shunt 112. A first alternating flux provided by the input winding 132 is thus primarily directed through a first magnetic loop which includes the first C-core and the magnetic shunt 112, and a second alternating flux provided by the output winding 136 is primarily directed through a second magnetic loop which includes the second Come and the magnetic shunt 112. A third magnetic loop, which effectively directly couples the input and output windings only when the magnetic shunt 112 saturates due to the vector sum of the first and second parallel alternating fluxes flowing through the magnetic shunt, is provided by the first and second C-cores and the portions of the magnetic shunt which couple the aligned ends of the C- cores.

The manufacture and assembly of the core-form parametric regulating transformer 130 is greatly facilitated by the construction shown in FIG. 7, as the non-magnetic gaps 120 and 122 in the second or output magnetic loop are formed without machining, and they may be increased or decreased in dimension by merely changing the thickness dimension of the insulating spacer member 118.

FIGS. 8, 9 and 10 illustrate an embodiment of the invention which illustrates the use of a magnetic shunt with shell-form magnetic core construction. More specifically, FIG. 8 is a perspective view. of a magnetic core 150 for a shell-form parametric regulating transformer, which utilizes a discrete magnetic shunt 152, formed of a plurality of stacked metallic, magnetic laminations 154, first and second wound E-shaped core elements 156 and 158, respectively, and insulating spacer means 160 which establishes and maintains nonmagnetic gaps 162, 164 and 166 between the ends of the legs of the second core portion 158 and the magnetic shunt 152.

The first and second substantially E-shaped core elements 156 and 158 may be formed by winding a strip of grain oriented silicon steel to form two side-by-side core elements, and then winding a plurality of turns of the magnetic strip about the side-by-side core elements, to provide a wound magnetic core structure such as illustrated in FIG. 2. However, instead of cutting the magnetic core as illustrated in FIG. 2, it is cut transversely to the leg portions, and it may be cut off-center in order to provide window volume according to the relative volumes of the input and output windings to be assembled with the magnetic core.

The first substantially E-shaped core element 156 includes first, second and third leg portions 168, 170 and 172, which are joined by a back portion 173, and the second substantially E-shaped core element 158 includes first, second and third leg portions 174, 176 and 178, which are joined by a back portion 179. In the assembly of the magnetic core 150, an input winding (not shown) is telescoped over the second or inner leg portion 170 of the E-shaped core element 156, and the substantially E-shaped core element 156 has its out ends butted tightly against one side of the shunt 152, with the side of the magnetic shunt selected preferably being one of the sides formed by the edges of the stack of laminations which make up the magnetic shunt.

An output winding (not shown) is telescoped over the second or inner leg portion 176 of the substantially E-shaped core element 158, but instead of butting the cut ends of the legs of core element 158 tightly up against the magnetic shunt 152, the ends are spaced from the magnetic shunt by a predetermined dimension. The insulating spacer means 160 is disposed between the ends of the core element 158 and the magnetic shunt 152, to establish and maintain the desired gap dimension for the gaps 162, 164 and 166.

In the assembly of the magnetic core 150, the cut ends of the E-shaped core elements 156 and 158 are aligned, just as they were prior to cutting, enabling the I resulting assembly to be easily banded to hold the various core elements and windings in assembled relation.

FIG. 9 is a perspective view of a magnetic core which is similar to the magnetic core 150 shown in FIG. 8 except the two E-shaped core elements are formed of a plurality of E-shaped laminations bonded together in stacks. Like reference numerals in FIGS. 8 and 9 indicate like components, and like reference numerals except for a prime mark in FIG. 9 indicate like func tions but a slightly modified structures.

More specifically, magnetic core 150 includes a magnetic shunt 152 and insulating spacer member 160, as hereinbefore described relative to FIG. 8, and first and second substantially E-shaped core elements 156' and 158, respectively. The first E-shaped core element 156' is constructed of a plurality of substantially E- FIG. is a partially schematic view of a shell-form parametric regulating transformer 180 constructed with the magnetic core 150' shown in FIG. 9, but it will be understood that the assembly would be the same using the magnetic core 150 shown in FIG. 8. An input winding 182 is disposed about the intermediate leg portion 170' of the first E-shaped core element 156', with the input winding 182 being adapted for connection to a source 184 of alternating potential. The first E- shaped core element 156 has the ends of its outwardly extending legs butted tightly against one side of the magnetic shunt 152.

An output winding 186 is disposed on leg 176 of the second E-shaped core element 158', a capacitor 188 is connected to the output winding 186 to provide a tank circuit, and the output winding is adapted for connection to a load circuit 190. This example again illustrates that the capacitor and load voltages need not be the same with the load circuit 190 being connected across only a predetermined portion of the output winding 186.

The insulating spacer member 160 is disposed on the side of the magnetic shunt 152 which is opposite to that associated with the first substantially E-shaped core element 156, and the second E-shaped core element 158' is butted against the insulating spacer member 160 such that its legs are aligned with the legs of the first E-shaped core element 156.

A first alternating flux provided by the input winding 182 divides substantially equally to circulate about the windows or openings 182 and 183, proceeding, on one half cycle, through the leg 170', dividing and proceeding in opposite directions through the magnetic shunt 152, through the outer leg portions and into the back portion 156 and then returning to the intermediate leg 170'. On the next half cycle, the flux circulation will be in the opposite direction. A second alternating flux in the magnetic core is provided by the output winding 186, with the flux, on one half cycle, proceeding out of the intermediate leg portion 176' and dividing equally to flow in opposite directions through the magnetic shunt 152, in the same directions as the first alternating flux provided by the input winding 182. This flux then enters the outer legs 174 and 178', proceeds through the back portion 158, and returns to the intermediate leg portion 176', thus encircling the two windows 185 and 187. The input and output windings 182 and 186 are effectively isolated from one another, until the vector sum of the first and second alternating fluxes in the magnetic shunt 152 saturate the magnetic shunt 152, forcing the first alternating flux to link the output winding 186 for the short interval of saturation, transferring energy into the tank circuit to sustain its oscillation.

The manufacture and assembly of the shell-form parametric regulating transformer 180 shown in FIG. 10 is greatly facilitated by the disclosed structure, as the non-magnetic gaps 162, 164 and 166 between the second core element 158' and the magnetic shunt 152 are formed without machining, and the dimensions of these gaps may be increased or decreased by merely changing the thickness dimension of the insulating spacer member 160. The insulating spacer member 160 may be a single sheet, as illustrated, or three separate insulating spacer members may be used, if desired.

FIGS. 11, 12 and 13 illustrate another embodiment of the invention which uses a magnetic shunt with shellforrn magnetic core construction. In the shell-form magnetic core structure shown in FIGS. 8, 9 and 10, the three leg portions of the E-shaped core elements all have the same cross-sectional area. Thus, the outer portions of the magnetic loops have one-half the flux density of the inner portions of the magnetic loop, which has the advantage of reducing iron losses, but the disadvantage of requiring more iron. If it is desired to work all of the iron at the same flux density, the middle leg of the E-shaped core elements should have a width dimension which is twice that of the outer leg portions. FIG. 11 illustrates how this may be easily accomplished using wound type magnetic cores, while FIG. 12 illustrates a stacked magnetic core which provides the same result.

More specifically, FIG. 11 is a perspective view of a magnetic core 200 for a shell-form parametric regulating transformer, which utilizes a discrete magnetic shunt 202 which is formed of a plurality of laminations 204 which are stacked and bonded together to maintain the integrity of the magnetic shunt. Magnetic core 200 has first and second substantially E-shaped core elements 206 and 212, with the first E-shaped core element 206 being formed of two C-cores 208 and 210 which are assembled in side-by-side relation such that their adjoining leg portions form a single intermediate leg 211. The remaining leg portions of the C-cores 208 and 210 provide the outer legs 209 and 213 of the E- shaped core element. The second substantially E- shaped core element 212 includes first and second C- cores 214 and 216, disposed in side-by-side relation, with the adjoining leg portions of the two C-cores providing the intermediate leg portion 217 of the E- shaped element. The remaining leg portions of the C- cores 214 and 216 provide outer leg portions 215 and 219 of the E-shaped core element. The four C-cores required to construct the magnetic core 200 may be formed by winding magnetic, metallic strip material to provide'two magnetic loops each having the desired window opening and required number of nested lamination turns, and then the two loops are severed, preferably off-center, as hereinbefore explained, to provide C-cores. For example, the C-cores 208 and 214 may be formed from a single magnetic loop, and the C- cores 210 and 216 may be formed from a single magnetic loop. It will be noted that this structure provides inner leg portions 211 and 217, upon which the input and output windings are disposed, which have twice the cross-sectional area of the outer leg portions of the magnetic core elements.

FIG. 12 is a perspective view of a magnetic core 200' which is similar to the magnetic core 200 shown in FIG. 11, except the two substantially E-shaped core elements 206 and 212 are formed of substantially E- shaped laminations, stacked and bonded together. Like reference numerals in FIGS. 11 and 12 indicate like components, and like reference numerals except for a prime mark in FIG. 12 indicate like functions but slightly modified structure. Magnetic core 200' shown in FIG. 12 is similar to the magnetic core shown in FIG. 9, except the width of the intermediate leg portions 211 and 217' is twice the width of the outer leg portions of the E-shaped laminations, while in the magnetic core shown in FIG. 9 the intermediate leg portions have the samewidth dimension as the outer leg portions.

FIG. 13 is a partially schematic view of a shell-form parametric regulating transformer 226 constructed with the magnetic core 200 shown in FIG. 12, but the construction would be the same using the magnetic core 200 shown in FIG. 11. An input winding 228 is disposed about intermediate leg portion 211 of the first E-shaped core element 206, and it is adapted for connection to a source 230 of alternating potential. The outwardly extending ends of the E-shaped element 206 butt tightly against the magnetic shunt 202.

An output winding 232 is disposed on intermediate leg portion 217 of the second E-shaped core element 212, and a capacitor 234 is connected across the output winding 232 to provide a tank circuit. In this embodiment, a separate load winding 236 is provided, which is also disposed about the intermediate leg portion 217', which winding is connected to a load circuit 238. However, a single output and load winding may be utilized, as shown in other embodiments of the invention. The operation of the shell-form transformer 226 is the same as hereinbefore described relative to the shellform transformer 180, which is illustrated in FIG. 10.

FIG. 14 is a perspective view, shown partially in phantom, of a core-form parametric regulating transformer 250 constructed according to still another embodiment of the invention. Transformer 250 includes a magnetic core 252 of the stacked type, shown partially completed, and input and output windings 254 and 256, respectively. The input and output windings 254 and 256 are shown in phantom to more clearly illustrate the construction of the magnetic core 252.

Magnetic core 252 includes a plurality of stacked or superposed layers 258 of metallic, magnetic laminations, such as 12 mil, grain oriented steel for 60 Hz. applications, with each layer of laminations including a modified E-shaped lamination 260 and an L-shaped lamination 262. The E-shaped lamination 260 includes first, second and third spaced-parallel leg portions 264, 266 and 268, respectively, joined by a back or yoke portion 270, with the third leg portion 268 having a shorter length dimension than the first and second leg portions 264 and 266. The L-shaped lamination 262 includes first and second connected portions 272 and 274, respectively, with portion 272 functioning as a yoke portion of the magnetic core and with the second portion 274 cooperating with the third leg 268 of the E- shaped lamination to complete a leg portion of the magnetic core, which leg portion functions as the output leg upon which the output winding 256 is disposed.

In the assembly of each layer of laminations, the ends of the first and second leg portions 264 and 266 of the E-shaped lamination butt against one side of the first portion 272 of the L-shaped lamination 262. The portions 268 and 274 of the E- and L-shaped laminations which cooperate to provide the output leg of the mag- 'netic core 252, are dimensioned to provide a gap 276 between their aligned ends, such as a gap having a dimension of mils per square inch of cross-sectional area of the output leg. The gap 276 is oriented such that its midpoint bisects dimension 278 of the magnetic core, i.e., that dimension between the outer surfaces of the yoke portions 270 and 272 of the E- and L-laminations. This orientation of the gap 276 enables the layers to be flipped over from layer to layer while maintaining the location and dimension of the gap 276. In other words, with the top layer oriented as illustrated in FIG. 14, the next layer which is referenced 280 and illustrated outside of the assembled laminations and windings, will have its E- and L-laminations 260' and 262', respectively, in rotational symmetry with the E- and L-laminations of the top layer, about an axis 282 which passes perpendicularly through the first and second leg portions of the E-lamination and through the gap, with arrow 284 illustrating how layer 280 has been rotated about this axis.

In the assembly of transformer 250, the windings 254 and 256 are placed in a fixture and the E- and L- laminations are built-up about the windings. First, an E- lamination would be inserted with its first and third leg portions entering the openings in the input and output windings, respectively, from one end of the windings, and the L-lamination would be placed adjacent to the opposite ends of the windings such that the ends of the first and second legs of the E-lamination butt against one side of the first portion 272 of the L-lamination, and the second portion 274 of the L-lamination enters the opening in the output winding to complete the output leg of the layer while establishing the gap 276 therein. The next layer of laminations would then be placed in position, after flipping them over, and placing them at opposite ends of the input and output windings, compared with their positions in the previous layer, with the first and third legs of the E-lamination still entering the input and output windings, and with the portion 274 of the L-lamination entering the output winding. This stacking procedure is repeated until the required stack build dimension is achieved. The E- and L'laminations may all have openings therein, such as openings 290 in the L-lamination and openings 292 in the E-lamination, through which bolts may be inserted when the magnetic core has been completed, to hold the laminations and input and output windings in the desired assembled relation. The gap 276 is automatically formed is this embodiment of the invention, within the output winding 256. The magnetic core construction of this embodiment makes it practical to easily change the dimensions of the gap after the magnetic core is assembled, by making the holes in the laminations larger than the bolts, or making the holes elongated. Thus, the laminations may be tapped into the desired positions and them clamped with the bolts. A varnish dip will then lock the laminations together.

If it is desired to reduce the cross-sectional area of the inner leg portion of the magnetic cores 252, compared with the cross-sectional area of the outer leg portions, the width dimension of the inner leg portion of the E-shaped laminations may be reduced, or the width dimensions of the legs may be the same, with an effective reduction in cross-sectional area being achieved by forming a notch 294 in the intermediate leg of the E- shaped lamination, which effectively reduces the crosssectional area of the intermediate leg portion. Another approach would be to utilize a certain number of the E- type laminations, which have the intermediate leg portion of the E removed, which laminations would be interspersed with the other laminations.

In summary, there has been disclosed new and improved parametric regulating transformers, and methods of constructing same, which establish a nonmagnetic gap in the output region of the transformer without requiring a machining step. Further, the gap may be established and changed at will, merely by changing the dimension of the spacer member, enabling unskilled personnel to quickly and easily establish the required operating characteristics of the transformers.

I claim as my invention:

1. A parametric regulating and filtering transformer, comprising:

a magnetic core having first, second and third separable sections, input and output windings disposed in inductive relation with said first and third sections, respectively,

said first section being butted against the second section to provide at least two spaced joints therewith and at least one magnetic loop, said third section being disposed adjacent to, but spaced from, said second section to provide at least one magnetic loop with the second section having two gaps therein, and at least one magnetic loop with the first section having two gaps therein,

spacer means disposed in the gaps between the second and third sections, to maintain predetermined gap dimensions,

means holding the first, second and third sections of the magnetic core in assembled relation,

and a capacitor connected to the output winding to provide a tank circuit.

2. The transformer of claim 1 wherein the gaps formed between the second and third sections are in a common plane.

3. The transformer of claim 1 wherein the first and third sections include the input and output leg of the magnetic core, and the second section includes the saturating leg.

4. The transfonner of claim 3 wherein the joints between the first and second sections lie in a common plane which is parallel with the axis of the input leg, and the gaps between the second and third sections are in a common plane parallel with the axis of the output leg.

5. The transformer of claim 3 wherein the second section also includes substantially all of the yoke portions of the magnetic core which interconnect the ends of the input, output and saturating legs.

6. The transformer of claim 1 wherein the magnetic core includes a plurality of nested turns of magnetic, metallic laminations.

7. The transformer of claim 3 wherein the second section is substantially rectangular in cross-sectional configuration, with the first and third sections including yoke portions which interconnect the ends of the input, output and saturating leg portions of the magnetic core.

8. The transformer of claim 7 wherein the magnetic core includes a plurality of nested turns of magnetic, metallic laminations.

9. The transformer of claim 7 wherein the magnetic core includes a plurality of flat, superposed layers of metallic, magnetic laminations.

10. The transformer of claim 1 wherein the first section is substantially E-shaped, having an intermediate leg portion and two outer portions, forming three spaced joints and two magnetic loops with the second section, with the input winding being disposed about the intermediate leg portion, and the third section is substantially E-shaped having an intermediate portion and two outer leg portions, forming two loops with the second section, each having two gaps therein, with the output winding being disposed on the intermediate leg portion of the third section.

11. The transformer of claim 10 wherein the intermediate leg portions of the first and third sections have the same width dimension as their outer leg portions.

12. The transformer of claim 10 wherein the intermediate leg portions of the first and third sections have twice the width dimension as their outer leg portions.

13. The transformer of claim 10 wherein the magnetic core includes a plurality of nested lamination turns formed of magnetic, metallic strip material.

14. The transformer of claim 10 wherein the magnetic core includes a plurality of flat, superposed layers of metallic laminations.

15. The transformer of claim 10 wherein the E- shaped first and third sections each include two substantially C-shaped loops disposed side-by-side, with their intermediate leg portions being formed of adjacent portions of the two C-shaped loops.

16. The transformer of claim 10 wherein the second section has a substantially rectangular cross-sectional configuration, and includes a plurality of flat, superposed magnetic metallic laminations.

17. A parametric regulating and filtering transformer, comprising:

a magnetic core having a plurality of superposed layers of laminations which define first, second .and third parallel leg portions and connecting yoke portions,

each of said layers including a substantially E-shaped lamination having first and second outer leg portions and an intermediate leg portion, with the second outer leg portion having a shorter longitudinal dimension than the first outer leg portion, and a substantially L-shaped lamination having first and second portions, with the first and intermediate leg portions of the E-lamination butting against the first portion of the L-lamination, and with the ends of the second portion of the L- lamination and the second outer leg portion of the E-lamination being aligned but spaced apart by a predetermined dimension to provide a predetermined gap, with the midpoint of the gap falling on the central axis of the layer which is perpendicular to the first outer and intermediate leg portion of the E-shaped lamination,

alternate layers of said magnetic core having their E- and L-laminations similarly oriented, with the remaining layers being in rotational symmetry with said alternate layers about the central axis of the alternate layers, to align the gaps in the layers and provide a gap in the third leg of the magnetic core,

input and output windings disposed in inductive relation with the first and third leg portions, respectively, of said magnetic core,

and a capacitor connected to said output winding to provide a tank circuit. 

1. A parametric regulating and filtering transformer, comprising: a magnetic core having first, second and third separable sections, input and output windings disposed in inductive relation with said first and third sections, respectively, said first section being butted against the second section to provide at least two spaced joints therewith and at least one magnetic loop, said third section being disposed adjacent to, but spaced from, said second section to provide at least one magnetic loop with the second section having two gaps therein, and at least one magnetic loop with the first section having two gaps therein, spacer means disposed in the gaps between the second and third sections, to maintain predetermined gap dimensions, means holding the first, second and third sections of the magnetic core in assembled relation, and a capacitor connected to the output winding to provide a tank circuit.
 2. The transformer of claim 1 wherein the gaps formed between the second and third sections are in a common plane.
 3. The transformer of claim 1 wherein the first and third sections include the input and output leg of the magnetic core, and the second section includes the saturating leg.
 4. The transformer of claim 3 wherein the joints between the first and second sections lie in a common plane which is parallel with the axis of the input leg, and the gaps between the second and third sections are in a common plane parallel with the axis of the output leg.
 5. The transformer of claim 3 wherein the second section also includes substantially all of the yoke portions of the magnetic core which interconnect the ends of the input, output and saturating legs.
 6. The transformer of claim 1 wherein the magnetic core includes a plurality of nested turns of magnetic, metallic laminations.
 7. The transformer of claim 3 wherein the second section is substantially rectangular in cross-sectional configuration, with the first and third sections including yoke portions which interconnect the ends of the input, output and saturating leg portions of the magnetic core.
 8. The transformer of claim 7 wherein the magnetic core includes a plurality of nested turns of magnetic, metallic laminations.
 9. The transformer of claim 7 wherein the magnetic core includes a plurality of flat, superposed layers of metallic, magnetic laminations.
 10. The transformer of claim 1 wherein the first section is substantially E-shaped, having an intermediate leg portion and two outer portions, forming three spaced joints and two magnetic loops with the second section, with the input winding being disposed about the intermediate leg portion, and the third section is substantially E-shaped having an intermediate portion and two outer leg portions, forming two loops with the second section, each having two gaps therein, with the output winding being disposed on the intermediate leg portion of the third section.
 11. The transformer of claim 10 wherein the intermediate leg portions of the first and third sections have the same width dimension as their outer leg portions.
 12. The transformer of claim 10 wherein the intermediate leg portions of the first and third sections have twice the width dimension as their outer leg portions.
 13. The transformer of claim 10 wherein the magnetic core includes a plurality of nested lamination turns formed of magnetic, metallic strip material.
 14. The transformer of claim 10 wherein the magnetic core includes a plurality of flat, superposed layers of metallic laminations.
 15. The transformer of claim 10 wherein the E-shaped first and third sections each include two substantially C-shaped loops disposed side-by-side, with their intermediate leg portions being formed of adjacent portions of the two C-shaped loops.
 16. The transformer of claim 10 wherein the second section has a substantially rectangular cross-sectional configuration, and includes a plurality of flat, superposed magnetic metallic laminations.
 17. A parametric regulating and filtering transformer, comprising: a magnetic core having a plurality of superposed layers of laminations which define first, second and third parallel leg portions and connecting yoke portions, each of said layers including a substantially E-shaped lamination having first and second outer leg portions and an intermediate leg portion, with the second outer leg portion having a shorter longitudinal dimension than the first outer leg portion, and a substantially L-shaped lamination having first and second portions, with the first and intermediate leg portions of the E-lamination butting against the first portion of the L-lamination, and with the ends of the second portion of the L-lamination and the second outer leg portion of the E-lamination being aligned but spaced apart by a predetermined dimension to provide a predetermined gap, with the midpoint of the gap falling on the central axis of the layer which is perpendicular to the first outer and intermediate leg portion of the E-shaped lamination, alternate layers of said magnetic core having their E- and L-laminations similarly oriented, with the remaining layers being in 180* rotational symmetry with said alternate layers about the central axis of the alternate layers, to align the gaps in the layers and provide a gap in the third leg of the magnetic core, input and output windings disposed in inductive relation with the first and third leg portions, respectively, of said magnetic core, and a capacitor connected to said output winding to provide a tank circuit. 